Cancer Therapy: Preclinical Phenylmethimazole Decreases Toll-Like Receptor 3 and Noncanonical Wnt5a Expression in Pancreatic Cancer and Melanoma Together with Tumor Cell Growth and Migration

Purpose: To evaluate whether (a) Wnt5a expression in pancreatic cancer and malignant melanoma cells might be associated with constitutive levels of Toll-like receptor 3 (TLR3) and/or TLR3 signaling; (b) phenylmethimazole (C10), a novel TLR signaling inhibitor, could decrease constitutive Wnt5a and TLR3 levels together with cell growth and migration; and (c) the efficacy of C10 as a potential inhibitor of pancreatic cancer and malignant melanoma cell growth in vivo. Experimental Design: We used a variety of molecular biology techniques including but not limited to PCR, Western blotting, and ELISA to evaluate the presence of constitutively activated TLR3/Wnt5a expression and signaling. 3-(4,5-Dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide-based technology and scratch assays were used to evaluate inhibition of cell growth and migration, respectively. TLR3 regulation of cell growth was confirmed using small interfering RNA technology. Nude and severe combined immunodeficient mice were implanted with human pancreatic cancer and/ or melanoma cells and the effects of C10 on tumor growth were evaluated. Results: We show that constitutive TLR3 expression is associated with constitutive Wnt5a in human pancreatic cancer and malignant melanoma cell lines, that C10 can decrease constitutive TLR3/Wnt5a expression and signaling, suggesting that they are interrelated signal systems, and that C10 inhibits growth and migration in both of these cancer cell lines. We also report that C10 is effective at inhibiting human pancreatic cancer and malignant melanoma tumor growth in vivo in nude or severe combined immunodeficient mice and associate this with inhibition of signal transducers and activators of transcription 3 activation. Conclusions: C10 may have potential therapeutic applicability in pancreatic cancer and malignant melanoma. Pancreatic cancer and malignant melanoma are difficult to treat and have poor prognoses. The American Cancer Society estimates that 37,680 people will have been diagnosed with pancreatic cancer in 2008, with an expected death rate of 92%. It is the fourth leading cause of cancer deaths in the United States and has an overall survival rate of <4%; most die within 6 months to 1 year from time of diagnosis. Malignant melanoma exceeds many other types of cancers in lost “years of life” because it is most prevalent in younger individuals. The poor prognosis is attributable to a highly invasive nature, metastases before discovery, and a poor response to chemotherapeutic and/or surgical intervention. Uncovering a potentially effective treatment for both carcinoma of the pancreas and malignant melanoma is therefore of importance, particularly if the therapy has a novel molecular basis and is applicable to both. The Wingless (Wnt) family of secreted glycoproteins control early developmental processes including cellular migration, differentiation, and proliferation (reviewed in ref. 1). “Canonical” Wnts modulate cell growth by increasing β-catenin levels, β-catenin nuclear localization, and binding to the LEF/TCF Authors' Affiliations: Edison Biotechnology Institute and Departments of Biomedical Sciences and Specialty Medicine, Appalachian Rural Health Institute, Diabetes Research Center, College of Osteopathic Medicine, Department of Chemical and Biomolecular Engineering and Biomedical Engineering Program, Russ College of Engineering and Technology, Ohio University, Athens, Ohio, Laboratory of Immunology, National Institute on Ageing, NIH, Gerontology Research Center, Baltimore, Maryland, Department of Pathology and Laboratory Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, Department of Medicine, Southern Illinois University, Springfield, Illinois, Hematology/Oncology, Cascade Cancer Center, Kirkland, Washington, and The Howard Hughes Medical Institute, University of Washington, Seattle, Washington Received 1/2/09; revised 2/25/09; accepted 3/12/09; published OnlineFirst